FIG. 1 shows a system 100 according to the prior art, which enables linking with mobile telephone network base stations 101, 102 and 103. The system comprises data transmission installations 104, 105, 106 and 107, which can be for example IP (Internet Protocol) routers, MPLS (Multiprotocol Label Switching) switches and/or Ethernet switches. Each data transmission installation can be a single device or a combination of several interconnected devices. Said data transmission installations are connected to each other over a local data transmission network 108. The data transmission network 108 comprises other data transmission installations and data transmission links therebetween. The system includes a gateway device 109, providing a link to a data transmission core network 110, a representative of which can be for example the global Internet. The gateway device 109 is connected over the data transmission installation 107 to the local data transmission network 108. The system 100 is in communication with a mobility management entity MME 111, which is adapted to maintain an up-to-date record for the locations of data terminals 112, 113 and 114 in a radio link network established by the base stations 101, 102 and 103. The mobility management entity 111 is connected to the gateway device 109 either directly or over a data transmission network. The mobility management entity 111 can also be incorporated in the gateway device 109. Each of the data terminals 112, 113 and 114 can be for example a mobile telephone or a palm computer.
The mobility management entity 111 is adapted, based on the locations of the data terminals 112, 113 and 114, to establish control data, on the basis of which the data transmission installations 104-107 and the gateway device 109 are able to create logical data transmission tunnels 115, 116 and 117 between the base stations 101, 102 and 103 and the gateway device 109. Said logical data transmission tunnels can be for example GTP-U (General Packet Radio Service Tunneling Protocol—User plane messages) data transmission tunnels, GRE (Generic Routing Encapsulation) data transmission tunnels, IPinIP (Internet Protocol in Internet Protocol) data transmission tunnels or data transmission tunnels implemented by Ethernet frames.
In the situation shown in FIG. 1, it is reasonable to assume, for example, that the data terminal 112 lies within a coverage range of the base station 101, the data terminal 113 lies within a coverage range of the base station 102, and the data terminal 114 lies within a coverage range of the base station 103. It is further reasonable to assume that the data terminal 112 has its communications transmitted in the logical data transmission tunnel 115, the data terminal 113 has its communications transmitted in the logical data transmission tunnel 116, and the data terminal 114 has its communications transmitted in the logical data transmission tunnel 117. In the event that for example the data terminal 112 passes from the coverage range of the base station 101 into the coverage range of the base station 102, the logical data transmission tunnel 115 will be cancelled and a corresponding new logical data transmission tunnel will be established between the gateway device 109 and the base station 102. A problem with the above-described type system 100 is that communications produced by data terminals and communications addressed thereto proceed by way of the gateway device 109. In other words, communications produced by data terminals and communications addressed thereto are forced to proceed by way of a single point in the data transmission network. As a result, the local data transmission network 108, the data transmission installation 107, and the gateway device 109 may be subjected to heavy loading, which calls for precautionary measures in the process of designing data transmission links and data transmission installations.